There have been a couple of occasions where I haven't been able to restart my macbook. Both times I've used this shortcut to restart but I am concerned about the state of the system upon reboot.

The log says:

kernel[0]: Previous Shutdown Cause: 5

a quick search didn't offer much.

Official Apple documentation lists the shortcuts, even the one to Power Off after 5secs without shutting down, with no explanation as to the consequences.

So, are there any documents that explain what exactly happens when this shortcut is used? Does it simply flush buffers, umounts filesystems and poweroff/restart....?


PS: I've already seen this question as regards to the code in the log.

  • The shutdown causes have never been properly documented but the rule of thumb is that 0 or positive numbers are normal and/or user initiated. Negative numbers are when the system shuts down because of a fault or hardware issue, like if you yanked the power cord from an iMac. – Mr Rabbit Jul 10 '14 at 20:17

Force restart is not safe mode of operation.

What happens is the power to the system is simply just cut off.

There is no soft landing in here, no flush buffers, umounts filesystems ect.. just brute force pull the plug.

You might want to consider following shortcuts in order before forcing it.

  1. Hold down the power button for 1.5 seconds - Show the restart / sleep / shutdown dialog in OS X Mavericks

  2. Hold down the power button for 5 seconds -Force the Mac to power off

  3. Command-Control-power button -Force the Mac to restart

As said, it is not safe mode, so frequent use can lead to multitude of problems. It is not possible to exactly specify what can happen, but results could be as bad as damage to the computer, mostly to the hard drive.

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  • You talking about forcing Power Off by holding power button for 5 secs. It works like with PCs where power is simply turned off and yes it is dangerous. Hence why I mentioned that it appears in Apple's docs but does not mention that it is dangerous. – Vic Jul 12 '14 at 18:49
  • @Vic What I am saying one should always try the option 1, all others can damage the computer. – Ruskes Jul 12 '14 at 19:02

My experience over many years on many Macs is that this does not generally cause problems. In the early days of PCs it could kill a machine through drive corruption but Macs have always been relatively robust. Theoretically it is not ideal but I have never had a problem. Startup can be quite slow after such a restart as I suspect there is disk checking etc. going on during the restart. It wouldn't hurt to Verify/Repair Disk Permissions (in Disk Utility) after a forced restart - something that should be done occasionally anyway - but I don't believe forcing a restart need be a big concern.

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